There is currently a strong trend to replace conventional lighting devices with lighting devices based on SSL technology for reasons of energy efficiency and operational lifetime. An example of a lighting device of the latter type is the light emitting diode (LED) tube lamp disclosed in US 2014/0009923 A1. Elongated lighting devices such as lighting tubes usually have a row of LEDs on a circuit board supported by a metal frame or similar inside an elongated housing. The housing can be made of glass, like in US 2014/0009923 A1, but for some applications it should be plastic.
A common problem with plastic housings is that they may over time become slightly curved due to creep caused by the gravitational force. Further efforts aimed at finding ways that help to prevent lighting devices with plastic housings from losing their shape over time are warranted.
One solution to this problem is to increase the dimensions of the metal frame, so as to provide additional structural strength to the lighting device. However, such an approach will make the lighting device heavier, and also reduce the amount of available space inside the tube.